Austin has this great tradition of celebrating the bats that live there every year. Millions of bats live under the Congress St. bridge and fly out everyday at dusk. One day a year the whole bridge is shut down and fills up with people going bat watching. They also have tents of vendors, food trucks and bat costume contests.
Such a fun experience, but you can do go almost any time around dusk and watch the bats with less crowds. I'm pretty sure you can dress up too and no one would look at you funny here.